Vertical transmission of Neospora caninum in BALB/c mice determined by polymerase chain reaction detection.

Vertical transmission of Neospora caninum was evaluated in BALB/c mice using an N. caninum-specific polymerase chain reaction (PCR) assay as a means of detecting parasite transmission to offspring. BALB/c mice were infected with the NC-1 isolate of N. caninum during pregnancy (days 8-15 gestation). Transmission of parasite, detected by PCR, was determined in 2- to 23-day-old offspring. When dams were infected on days 13-15 of gestation, transfer of parasites was detected in only a proportion of the litter. Infection between days 8 and 12 of gestation resulted in a high frequency of parasite transmission; every offspring from all litters was infected. The tissue locations of parasites in pups of different ages were determined. In young pups (2- to 4-days-old), the predominant sites of infection were the lungs and the brain. In older pups (7- and 23-days-old) the predominant site of infection was the brain. This study shows that PCR may be useful for evaluation of candidate vaccines against horizontal N. caninum infection, vertical transmission, or both.